The detection of a drug-resistant bug has surged at public hospitals this year as authorities intensify their clinical screening efforts, the latest data shows.

Queen Elizabeth Hospital in Yau Ma Tei was the worst hit, having detected the Vancomycin-resistant Enterococcus (VRE) in 300 patients - or more than 70 per cent of the cases across the city's public hospitals.

Dr Tsang Ngai-chong, the Hospital Authority's chief infection control officer, attributed the high numbers found at Queen Elizabeth to increased testing. "VRE might have evaded detection [previously when] we did not carry out controlled laboratory clinical tests," he said yesterday in releasing the authority's data.

Ho Pak-leung, University of Hong Kong microbiologist, said the figures indicated an outbreak at the hospital and could imply a failure in containing infectious diseases. "The authority should review its plan in containing the outbreak. When a hospital is looking at such a serious situation, somebody should take the responsibility," he said.

Ho sent a letter to health minister Dr Ko Wing-man, urging him to oversee the formation of a better strategy and more open access to infected patients' data.

VRE is a bacteria often associated with outbreaks in health institutions. It is resistant to multiple drugs and can be carried by healthy people, who feel the effects only when they are sick or injured. No one has been killed by the bug so far this year.

Ho warned that VRE presented a significant risk to patients who were old, chronically ill, or at their illnesses' terminal stage.

Tsang said the infection rate, now at 4.2 per cent of 600 carriers recently tested, was considered "very low". He said the authority had taken various measures to stop the spread of the bacteria, including conducting a programme on hand hygiene and decontaminating hospitals with new disinfectants.

The intensified testing saw 40,000 patients screened in public hospitals since 2011, of which 911 were confirmed infected. Queen Elizabeth together with other, smaller hospitals in central Kowloon detected the bacteria in 558 patients. The remaining 353 cases were found in other public hospitals.

This year, Queen Elizabeth alone has seen 396 cases up to May, pushing the overall numbers at all public hospitals to 543. The total already exceeds the 246 cases recorded in all public hospitals in the whole of last year, and the 122 cases in 2011.

Tsang said Hong Kong typically saw a VRE prevalence rate of 1 to 3 per cent, while Taiwan and the United States had more than 10 per cent. He said VRE was less worrying than another superbug, the methicillin-resistant Staphylococcus aureus (MRSA), as it had a lower mortality rate and could be treated by antibiotics.

Ho disagreed. "The situation should not be overlooked. There should be an investigation into why some hospitals are seeing more cases than others," he said.

This article appeared in the South China Morning Post print edition as Tests show superbug cases doubled